1. Field of the Invention
The invention relates to a method and apparatus for adjusting the true running path of the cutting edge of annular saw blades by exerting tensional forces thereon. More particularly, the adjustment method uses tensioning elements acting on the outer edge region of the saw blade to make sure the blade runs true.
2. Description of the Prior Art
For cutting thin slices or wafers from rod-type or block-type workpieces composed of semiconductors or oxidic materials such as, for example, silicon, germanium, gallium arsenide, gallium-gadolinium-garnet, sapphire or quartz, use is mainly made of internal-hole or annular saws. In annular saws, the saw blades are clamped in a holder at their outer edge. The inner edge of the saw blade is generally coated with a nickeldiamond coating and represents the actual cutting edge which removes material in the cutting process. At the same time, alignment of the saw blade to insure true running, in particular of the cutting edge, can be effected in the radial direction by means of the tensional forces exerted in the outer edge region on the saw blade. Suitable tensioning devices are described, for example, in German Patent specification Nos. 3,442,730 and 2,841,653, and U.S. Pat. Nos. 3,175,548 and 3,039,235.
It has long been known that it is very important to control the radial true running of the cutting edge as precisely as possible, and consequently the tensioning of the saw blade. On the one hand, this has a decisive effect on the cutting accuracy, and on the other hand, also on the service life of the saw blade. Normally, the saw blades are carefully clamped by hand, and the adjustment of the radial true running of the cutting edge ultimately depends on the manual skill of the operator concerned and is accordingly subject to the variations.